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The green catalytic system (Al2O3/H2O2/ethyl acetate) used in the oxidation of (R)-limonene has many advantages since the reagents have low cost, it is toxicity-free (no heavy metals and no toxic solvents are utilized), and water is the only by-product. The synthesized epoxide may have applications in several industrial segments like adhesives, polymers, resins, and others that require a clean process, especially as a precursor for medical biomaterial applications. An experimental design 23 with 17 assays (6 axial points and central point triplicate) has been carried out for the optimization of the conversion and selectivity towards limonene diepoxide. The assessed variables included the quantities of alumina, limonene, and hydrogen peroxide (70% aq). The analysis of variance (ANOVA) confirmed the validity of the mathematical model obtained with a 90% confidence interval in the studied range. The conversion and selectivity towards limonene diepoxide was >99%, with a reaction time of 10 h, showing the high efficiency of this catalytic system. FTIR, Raman, GC/MS, 1H, 13C, and HSQC NMR techniques confirmed the structure of the synthesized and purified limonene diepoxide.

In the present paper we described the oxidation of 2-butanol as a representative of secondary aliphatic alcohols. The oxidizing system FeCl3-H2O2 was used. A kinetic study of the oxidation reaction has been carried out. Different substituted pyrazines and pyrazoles, namely 2-pyrazinecarboxylic acid (PCA), 5-methyl-2-pyrazinecarboxylic acid (5MPCA), 2-methylpyrazine (2MPZINE), 3-(trifluoromethyl)pyrazole (3TFMPZOLE), 3-methylpyrazole (3MPZOLE) and 1-methylpyrazole (1MPZOLE) were added as cooperating ligands in aqueous solutions. DFT based calculations were also used in order to evaluate the different results obtained. Addition of PCA, 5MPCA and 3TFMPZOLE led to a better reaction performance, while the other ligands led to lower accumulation of products than the reaction without additives. Performed DFT studies suggested that the metal-ligand π-backbonding might be responsible for the reaction activity increase, while ligands more strongly bonded to Fe make it more difficult the access to the metal, leading to lower yields.

Activate carbon (AC) demand has increased worldwide, with application in adsorption, heterogeneous catalysis, and most recently as electrocatalyst support. However, while AC production from agro-industrial waste are widely researched, textile waste is neglected as raw material. In this study, cotton fabric was first applied as textile dye adsorbent after iron impregnation, which enhanced the adsorption capacity. The dye adsorbed fabric was than sequentially pyrolyzed at 800 °C for 2 h under N2 atmosphere, producing a magnetic mesoporous activated carbon (MAC) of 472 m2 g-1 BET surface area with 82% micropores and magnetization saturation of 34.2 emu g-1 deriving from encapsulated metallic αFe. This new simple and fast one-step carbonization, activation and iron incorporation method, has very low chemicals consumption and waste generation compared to the traditionally applied ones. The so produced MAC was loaded with 20 % Pd and tested for electrocatalyst properties: high density current for ethanol oxidation of 549 mA mg-1Pd, 1.37 times higher than using commercial Pd catalyst, lower onset potential of -0.48 V vs NHE. Application of the electrocatalyst for direct ethanol fuel cell achieved a high energy production of 27 mW cm-2 at 353 K.

The pretreatment of biomass represents a large energy expenditure in the production of sugar alcohols. Current research efforts are focused on integrating catalytic processes to decrease operating time and reduce energy and raw material consumption. In this work, the hydrolysis-hydrogenation of hemicellulose for xylitol production direct from corncob was studied. It was used two strategies of hydrogenation: H2 gas under pressure, and isopropanol as H2 donor. The importance of the presence of H2SO4 and 5% Ru/C catalyst in the reaction medium was analyzed. It was considered the use of H2 pressure (2 MPa) and employing isopropanol (water-isopropanol 1:3) as a source of hydrogen. The reaction products were determined by HPLC. The 5% Ru/C catalyst was active and selective for the conversion of xylose to xylitol. To promote the hydrolysis of the hemicellulose fraction of the corncob into xylose, the addition of acid was necessary. Under mild conditions (0.1% H2SO4, 413 K), xylose was detected as the main product, indicating the good selectivity of the first hemicellulose conversion step. A xylitol yield was 19% under H2 pressure while with isopropanol 7% was obtained. The intermediate purification step was eliminated because as xylose was formed it was simultaneously hydrogenated to produce xylitol in the presence of Ru catalyst. Cellulose remained intact in the solid residue and could be used to obtain other products, such as glucose, sorbitol, ethanol, or charcoal.

In this work, a highly acidic sulfonated carbon was obtained from eucalyptus kraft lignin, a byproduct from paper industry, and then used as catalyst in fructose dehydration. Reactions were performed employing dimethylsulfoxide (DMSO) as low cost/toxicity solvent and under microwave heating. The main product obtained was 5-hydroxymethylfurfural (5-HMF), a versatile platform compound that can be converted to several products of industrial interest. The catalyst is highly active to fructose dehydration and is able to convert 93.3% of the fructose (in a 10% m/v DMSO solution) with 98% of selectivity for 5-HMF in just 10 s at 393 K. Investigations about the catalyst dosage, reaction temperature and substrate concentration were carried out. In addition, the low-cost catalyst produced outperformed expensive commercial catalysts under the same conditions. After a simple regeneration process, the catalyst produced also can be recycled without significant loss in its catalytic activity.

Xylitol is one of the Top Value-Added chemicals from biomass released by DOE, with no petrochemical alternative. Industrially, this polyol is obtained by catalytic hydrogenation of xylose, a major component of hemicellulose. From xylitol it is possible to obtain various products, such as polyethylene glycol and ethylene glycol, and thus substitute fossil-based raw material. To reduce production costs and make the process environmentally friendly, it is necessary to reduce the stages of chemical conversion of lignocelluloses to xylitol. The present paper discusses the research advances focused on integrating several types of catalytic processes in a single container. The mechanism of catalytic hydrogenation of xylose to xylitol is detailed. The domain of the different parameters of the reaction will allow to increase the efficiency of the transformation of the biomass.

Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition-metal-free oxides, gallium oxide nanorods with small dimensions (9-52 nm length and 3-5 nm width) and fully accessible, high surface area (225 m(2) g(-1)) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity.

International audience; In the present work, dehydrodieugenol B (1) and its methyl ether (2), isolated from Nectandra leucantha twigs, were used as starting material for the preparation of two new derivatives (1a and 2a) containing an additional methoxycarbonyl unit on allyl side chains. Compounds 1a and 2a demonstrated activity against trypomastigotes (EC(50) values of 13.5 and 23.0 μM, respectively) and against intracellular amastigotes (EC(50) values of 10.2 and 6.1 μM, respectively). Additionally, compound 2a demonstrated no mammalian cytotoxicity up to 200 μM whereas compound 1a exhibited a CC(50) value of 139.8 μM. The mechanism of action studies of compounds 1a and 2a demonstrated a significant depolarization of the plasma membrane potential in trypomastigotes, followed by a mitochondrial membrane potential collapse. Neither calcium level nor reactive oxygen species alterations were observed after a short-time incubation. Considering the potential of compound 2a against T. cruzi and its simple preparation from the natural product 2, isolated from N. leucantha, this compound could be considered a new hit for future drug design studies in Chagas disease.

We report a new, straightforward and inexpensive sol-gel route to prepare boehmite nanorods [gamma-AlO(OH)-NR] with an average length of 23 nm +/- 3 nm, an average diameter of 2 nm +/- 0.3 nm and a high specific surface area of 448 m(2)/g, as evidenced by TEM and N-2-physisorption, respectively. The boehmite was converted to gamma-alumina with preserved nanorod morphology (gamma-Al2O3-NR) and high surface area upon calcination either at 400 or 600 degrees C. These nanostructured materials are active and selective heterogeneous catalysts for the epoxidation of alkenes with the environmentally friendly H2O2. The best catalyst, gamma-Al2O3-NR-400, showed to be versatile in the scope of alkenes that could be converted selectively to their epoxide and displayed enhanced reusability compared to previously reported alumina catalysts. Furthermore, the catalytic performance of the material was enhanced by optimising the reaction conditions such as the solvent and the type of hydrogen peroxide source. Under the optimised reaction conditions, the gamma-Al2O3-NR-400 catalyst displayed 58% cyclooctene oxide yield after 4h of reaction at 80 degrees C with full selectivity towards the epoxide product. The correlation between the catalytic activity of these materials and their physicochemical properties such as surface area, hydrophilicity and number and type of acid sites was critically discussed based on a detailed characterisation study.

In this work, we investigated the use of cotton scraps in natura and modified with iron nitrate,in the adsorption of one of the main water contaminants of the textile industries, the reactive black dye. Special attention was paid to the appropriate destination of the spent adsorbent, in compliance with the precepts of the circular economy. Cotton and polyester are excellent candidates for adsorbents and are produced on a large scale worldwide, but fabric wastes do not yet have a wellestablished method of application. We found that fabrics containing different types of fibers or colors maintain the ability to remove dye. The retention promoted by the cotton fabric in natura reached 18.8 mg g-1. After treatment with iron ions, there was an increase in the dye adsorption capacity to 31.0 mg g-1. In addition, the spent iron-containing adsorbent was pyrolyzed at 973 K, resulting in an activated magnetic carbon with a specific surface area ranging from 300 to 565 m2 g-1. Thus, it was possible to convert the used adsorbent into a new material with wide application possibilities.

International audience; The straightforward functionalization of sterically demanding alpha,alpha-disubstituted double bonds of beta-pinene, (-)-limonene and (-)-limonene terpenoids has been achieved via cross metathesis with internal olefins. The reactions are catalyzed by second generation ruthenium catalysts in dimethyl carbonate as green solvent or under neat conditions. This transformation provides a clean process for the access to functionalized bulky cyclic terpenes where the terminal double bond generates a trisubstituted olefin.

Both the catalytic production of 5-hydroxymethylfurfural (5-HMF) from carbohydrates and the use of a catalyst obtained from residues stand out for adding value to by-products and wastes. These processes contribute to the circular economy. In this work it was evaluated optimized conditions for 5-HMF production from fructose with high yield and selectivity. The reaction was catalyzed by an acidic carbon obtained from glycerol, a byproduct of the biodiesel industry. Special attention has been given to the use of dimethyl sulfoxide (DMSO) as a solvent and its influence on system activity, both in the presence and absence of O2. Glycerol's carbon with acidic properties can be effectively used as catalyst in fructose dehydration, allowed achieving conversions close to 100% with 5-HMF selectivities higher than 90%. The catalyst can be reused in consecutive batch runs. The influence of DMSO in the presence of O2 should be considered in the catalytic activity, as the stabilization of a reaction intermediate by the [O2:DMSO] complex is favored and, both fructose conversion and 5-HMF yield increase.

International audience; The straightforward functionalization of sterically demanding α,α-disubstituted double bonds of the natural products β-pinene and limonene via cross metathesis with symmetrical internal olefins is described. The reaction is catalyzed by Hoveyda-Grubbs type ruthenium catalysts in dimethyl carbonate as green solvent and makes possible the clean introduction of ester and nitrile groups in one step without formation of byproducts.

Acidic carbons were prepared by carbonization and in situ sulfonation of glycerin, a by-product from biodiesel production, and glycerol. The synthetic method used allowed the production of solids containing a large amount of surface functional groups, mainly sulfonic groups. The catalytic performance of the prepared materials was evaluated in reactions typically promoted by acidic catalysts. Conversions as high as 78% for the glycerol acetalization at room temperature and 85% for the glycerol etherification at 393 K were obtained. Furthermore we studied the reaction conditions of fructose dehydration using the prepared materials as catalysts, resulting in milder conditions than those found in the literature for this reaction using carbons as catalysts, with a 5-HMF yield close to 69%.

Biodiesel is one of the most common biofuels, and its production yields a large amount of glycerol as a by-product. It is necessary to develop new technologies for the use of this by-product, adding value to the biodiesel production chain. In this work we investigated glycerol oxidation under mild reaction conditions (air as oxidizing agent and base-free medium) promoted by suitable catalysts. We prepared mono- and bimetallic catalysts of platinum, copper and nickel in the form of nanoparticles by conventional heating and by an alternative method using microwave heating. The nanoparticles were dispersed in activated carbon and tested in glycerol oxidation aiming its valorization into molecules with high added value. Copper and nickel monometallic materials were not active in glycerol oxidation. Platinum monometallic and platinum–copper and platinum–nickel bimetallic materials showed catalytic activity, with platinum–nickel prepared by microwave heating being the most active material in reactions tested. This catalyst presented glycerol conversion of approximately 20% with a turnover number of 9465 in a reaction time of 6 h and 58% of selectivity to glyceric acid, the main product obtained. The best performance of platinum–nickel prepared by microwave heating catalyst was attributed to the probable formation of a metallic alloy between Pt and Ni, as evidenced by the decrease in the lattice parameter for PtNi bimetallic nanoparticles. The results showed that it was possible to obtain an active catalyst in glycerol oxidation reaction under mild conditions via a simple methodology using microwave heating, which demands 94% less time in comparison with conventional heating.

New copper(II) catalytic systems for the mild oxidative C–H functionalization of cycloalkanes and cycloalkenes were developed, which are based on a series of mixed-ligand aminoalcohol-dicarboxylate coordination polymers, namely [Cu2(μ-dmea)2(μ-nda)(H2O)2]n·2nH2O (1), [Cu2(μ-Hmdea)2(μ-nda)]n·2nH2O (2), and [Cu2(μ-Hbdea)2(μ-nda)]n·2nH2O (3) that bear slightly different dicopper(II) aminoalcoholate cores, as well as on a structurally distinct dicopper(II) [Cu2(H4etda)2(μ-nda)]·nda·4H2O (4) derivative [abbreviations: H2nda, 2,6-naphthalenedicarboxylic acid; Hdmea, N,N′-dimethylethanolamine; H2mdea, N-methyldiethanolamine; H2bdea, N-butyldiethanolamine; H4etda, N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine]. Compounds 1–4 act as homogeneous catalysts in the three types of model catalytic reactions that proceed in aqueous acetonitrile medium under mild conditions (50–60°C): (i) the oxidation of cyclohexane by hydrogen peroxide to cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone, (ii) the oxidation of cycloalkenes (cyclohexene, cyclooctene) by hydrogen peroxide to a mixture of different oxidation products, and (iii) the single-pot hydrocarboxylation of cycloalkanes (cyclopentane, cyclohexane, cycloheptane, cyclooctane) by carbon monoxide, water, and a peroxodisulfate oxidant into the corresponding cycloalkanecarboxylic acids. The catalyst and substrate scope as well as some mechanistic features were investigated; the highest catalytic activity of 1–4 was observed in the hydrocarboxylation of cycloalkanes, allowing to achieve up to 50% total product yields (based on substrate).

Ethanol obtained from sugarcane is an interesting biomass feedstock that is widely used as fuel and fuel additive. Another relevant biomass feedstock is acetol obtained from glycerol, the major byproduct of biodiesel manufacturing. Ethanol and acetol were oxidized by the Fe(ClO4)3-HClO4-H2O2 system in water at 60 °C with full conversions. Ethanol (0.1 M) oxidation yielded 0.058 M formic acid (HFO) and 0.085 M acetic acid (HAC), whereas acetol (0.1 M) oxidation provided 0.059 M HFO and 0.1 M HAC. On the basis of kinetic studies, the oxidation of these feedstocks followed different mechanisms. Ethanol oxidation followed a chain mechanism induced by hydroxyl radicals generated during the catalytic decomposition of H2O2 by Fe3+. Acetol oxidation, on the other hand, followed a non-chain process in which the complex formed between acetol (as substrate) and the catalyst played a decisive role, and interaction between this complex and H2O2 was the limiting stage. The activation energies for ethanol and acetol oxidation were 24.1 and 14.8 kcal/mol, respectively.

Hierarchical zeolite possessing MFI framework type was hydrothermally prepared using C22H45 − N+(CH3)2 − C6H12 − N+(CH3)2 − C6H13 as a structure-directing agent in a seed-assisted synthesis method. The nanosponge-like morphology was composed of a three-dimensional disordered network of MFI layers with 2.5 nm thickness supporting each other. Catalytic performance of the MFI nanosponge was investigated in glycerol etherification with tert-butyl alcohol in liquid phase and compared to conventional microporous MFI zeolite and MFI unilamelar nanosheet. The hierarchical zeolites were much more active, which can be attributed to the acid sites located on the external surfaces accessible for the reaction of bulky reactants.

α-Hydroxyacetone (acetol) which is easily produced from glycerol can be oxidized to other products of industrial interest. In this work the acetol oxidation by homogeneous cheap and green catalytic system FeCl3/H2O2 has been studied. Acetonitrile or water was used as solvent. Acetol (0.5 M) gave acetic acid (0.25 M) and formic acid (0.35 M) as the main products. Some amount of CO2 was also detected. For quantification of the CO2 amount, a novel method has been developed which uses GC–MS for monitoring the signals produced by the CO2 and argon (used as internal standard) present in the headspace of the reaction vessel. The formation of 0.028 M CO2 after 4 h under typical conditions was demonstrated. The effects of reactant concentration on the initial reaction rate were studied. The experiments in atmosphere of 16O2 and 16O2 + 18O2 led to the conclusion that molecular oxygen from atmosphere takes part in the reaction and these atoms are incorporated into the products.

Black carbon from coffee grounds (BCC) was treated with sulfuric acid (BCC-S) or fuming sulfuric acid (BCC-SF) and utilized as catalysts in glycerol etherification reactions. The BCC-SF showed a high amount of sulfur groups, about 8%. However, the treated BCC-S showed the lowest amount of sulfur groups, about 3%. Furthermore, these catalysts show high catalytic activity in the glycerol etherification with tert-butyl alcohol (TBA), the activity being higher for the BCC-SF. The yields for mono-tert-butyl glycerol (MTBG), di-tert-butyl glycerol (DTBG) and tri-tert-butyl-glycerol (TTBG) were very similar to those obtained using a commercial resin, Amberlyst-15. The yields for BCC-SF were about 40 and 20% for the MTBG and DTBG + TTBG, respectively. Furthermore, the acid black carbons showed high stability of the active groups and can be reused in consecutive reactions.

Oxidized and sulfonated-activated carbons (AC) were tested in the catalytic conversion of glycerol by acetalization reactions. The solids were treated with concentrated nitric acid and/or fuming sulfuric acid (AC, AC-N, AC-S, and AC-NS). The presence of sulfur and an increase in the acidity of the solids demonstrate the suitability of the oxidation as well as the sulfonation process, especially in the sample treated with concentrated nitric acid and fuming sulfuric acid (AC-NS). The best catalyst for the reaction of glycerol acetalization with phenylacetaldehyde was AC-NS, with a phenylacetaldehyde conversion of 95 % after 90 min at 383 K and selectivity of 88 and 12 %, respectively, to dioxolane and dioxane. These products can be used as hyacinth fragrance flavoring compounds. Furthermore, a contribution of homogeneous catalysis in these systems was not identified. Thus, we identified a possibility of glycerol conversion, a biodiesel by-product, into value-added products by suitable catalysts produced from activated carbons.

International audience; Stimulated by the strong interest in replacing fossil raw materials by renewable feedstocks in chemical industry, alkene metathesis of unsaturated bio-sourced olefins has been recently investigated with the objective of producing high-value molecules using green and atom economic strategies. It is due time to review what has been achieved in this field using terpenes and terpenoids as olefin metathesis partners. These substrates, derived from the isoprene structure, present different types of carbon-carbon double bonds that can be involved in self metathesis, ring closing metathesis, cross metathesis including ethenolysis, and ring opening metathesis. The successful achievements and remaining bottlenecks in this field will be discussed.

The efficient (turnover numbers attained 1200) oxidation of alkanes to the corresponding alkyl hydroperoxides by H2O2 in the presence of catalytic amounts of ferrocene proceeds in MeCN at 40–50 °C. Benzene is oxidized in the same system to phenol. An obligatory component of the catalytic system for both reactions is pyrazine-2-carboxylic acid (PCA) or trifluoroacetic acid (TFA). Kinetic study as well as selectivity parameters testified that the oxidation proceeds with the participation of hydroxyl radicals. In the case of PCA as a co-catalyst the initial rate W0 of the reaction with both cyclohexane and benzene depends quadratically on [Cp2Fe]0 whereas the two reactions in the presence of TFA are of half order in ferrocene. The ferrocene-catalyzed reaction of cyclohexane with H 2 O 2 16 in an atmosphere of labeled 18O2 gave after 2 h a mixture of labeled and unlabeled cyclohexyl hydroperoxide (total yield 20% based on starting cyclohexane) containing up to 69% of 18O (the analysis was after reduction of cyclohexyl hydroperoxide into cyclohexanol with PPh3).

The present work evaluated the effect of Pt, Pd and Ru catalysts supported on pillared clay (Al-Pilc) on the selectivity and products yielded in the hydrogenolysis of glycerol. The catalyst was prepared by aqueous suspension impregnation, with precursors Pt(NH3)4Cl2·0.68H2O, PdCl2 and RuCl3·1.37H2O, to obtain a nominal content catalyst of 2 wt%. They were characterized by specific surface area, temperature programmed reduction, X-ray diffraction, infrared spectroscopy of adsorbed pyridine, and pyridine temperature programmed desorption. As co-catalyst, the solid studied was Amberlyst 15. The hydrogenolysis of glycerol was performed in the liquid phase, typically at 393 K and 50 bar. The results indicate that the use of bifunctional metal–acid catalysts is a way to make the hydrogenolysis more effective because it favors the dehydration and hydrogenation reactions to produce 1,2-propanediol (1,2PD) and 1-propanol (1PO). Higher yield and a suitable selectivity to 1,2-propanediol were obtained for Ru/Al-Pilc.

Sulfonated niobia (HY-340 CBMM) and pillared clay (Fluka) were tested in the catalytic conversion of glycerol by etherification reactions. The solids were treated with concentrated fuming sulfuric acid (AS100 and NS100), and a 30% aqueous solution of this acid (AS30 and NS30). Both the presence of sulfur and the increase in the acidity of the solids demonstrate the suitability of the sulfonation process, especially in samples treated with concentrated fuming sulfuric acid. The best catalyst for the reaction of etherification with tert -butyl alcohol was AS100, with a glycerol conversion of 95% after 5 h at 393 K and yield of 60.3, 33.2 and 5.4%, respectively for mono- tert -butyl-glycerol (MTBG), di- tert -butyl-glycerol (DTBG) and tri- tert -butyl-glycerol (TTBG).

In this work, activated carbon (AC) was prepared from rice husk by chemical activation. AC was prepared using factorial design as a statistical tool to facilitate the process and to reach results that would not be possible changing one variable at a time. AC characterizations were performed by N 2 adsorption/desorption and surface group titulation. Some AC was obtained with high surface area, up to 1593 m 2 g − 1 , high mesopore volume, up to 1.22 cm 3 g − 1 , and surface acids, up to 4.4 mmol g − 1 . These characteristics are very important for AC application such as adsorption or acid catalysis. With this work, we were able to conclude that it is possible to prepare activated carbon from rice husk with high surface area, mesoporosity and surface acid groups, using factorial design as an efficient tool to plan the experiments.

Activated carbons prepared from agricultural waste were modified to introduce surface acid sites by treatment with HNO3 or H2SO4. These acid-functionalised materials were studied as heterogeneous catalysts for the solvent-free acetalisation of acetone with glycerol to produce 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal). The best catalyst was prepared by treatment with concentrated sulphuric acid and achieved 97% conversion of glycerol with high selectivity towards solketal by reaction with acetone at room temperature. The catalytic behaviour of the activated carbons was correlated with their physicochemical properties through characterization by N2-physisorption, XPS, elemental analysis, TGA and Boehm titration of the acid sites.

Sulfonated carbons were prepared from carbonized rice husk and further treatment with sulfuric acid (TC-6M, sulfuric acid 6 mol L–1 under reflux, TC-L, concentrated 96% sulfuric acid under reflux, TC-V, vapor of concentrated 96% sulfuric acid). The catalytic activity of carbons was evaluated in esterification of glycerol with acetic acid (AA) and etherification of glycerol with tert-butyl alcohol (TBA). Only the TC-L carbon showed a significant amount of sulfur in its composition (2.2 mmol g–1). This catalyst also had the highest total acidity (5.8 mmol g–1) and improved the best catalytic performance in glycerol esterification and etherification. In the esterification reaction of glycerol, 90% conversion was observed after 5 h of reaction, with selectivities of 11%, 52%, and 37% to mono-, di-, and tri-glycerides, respectively. In the etherification of glycerol, after 4 h of reaction a conversion of 53% was achieved, with 25% selectivity to di- and tri-tert-butylglycerol. Thus, the use of sulfonated carbo...

Sulfonated carbon-based catalysts were prepared from agroindustrial wastes (sugar cane bagasse, coconut husk, and coffee grounds). These catalysts showed high activity for glycerol etherification with tert-butyl alcohol. Yields of mono-tert-butyl glycerol (MTBG), di-tert-butyl glycerol (DTBG), and tri-tert-butyl-glycerol (TTBG) were higher than that obtained using Amberlyst-15 commercial resin. At 393 K and 5 wt % catalyst loading, glycerol conversion and selectivity to DTBG+TTBG after 4 h reaction time were 80.9% and 21.3%, respectively, with the sugar cane bagasse-based catalyst. Both catalytic activity and selectivity were affected by the presence of water in the reaction medium. However, the flexible and hydrophilic structure of the oxidized carbon allows the adsorption of water without compromising the activity of acid sites.

Niobium-aluminum-based catalysts were synthesized by a sol–gel process and successfully applied to the reaction of acetalization of acetone with glycerol yielding 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) and 2,2-dimethyl-1,3-dioxan-5-ol. The synthesis procedure was developed using high-throughput techniques and the materials prepared with molar ratio1 Metal (1Nb:xAl): 100H2O: 1.5NH4OH (in which x = 1, 0.6, 0.3, 0.1 and 0.05) were selected to be further investigated. The obtained series of mixed oxides displayed high catalytic activity reaching glycerol conversion up to 84%, with 98% of selectivity towards solketal. The physicochemical properties of the investigated catalysts were characterized by N2-adorption/desorption, thermal analysis, X-rays diffraction, FTIR and Raman spectroscopy, and by adsorption of pyridine monitored by FT-IR spectroscopy and TGA. The catalysts are truly heterogeneous and can be reused in consecutive runs without loss of activity.

New hexanuclear nickel(II) silsesquioxane [(PhSiO1.5)12(NiO)6(NaCl)] (1) was synthesized as its dioxane-benzonitrile-water complex (PhSiO1,5)12(NiO)6(NaCl)(C4H8O2)13(PhCN)2(H2O)2 and studied by X-ray and topological analysis. The compound exhibits cylinder-like type of molecular architecture and represents very rare case of polyhedral complexation of metallasilsesquioxane with benzonitrile. Complex 1 exhibited catalytic activity in activation of such small molecules as light alkanes and alcohols. Namely, oxidation of alcohols with tert-butylhydroperoxide and alkanes with meta-chloroperoxybenzoic acid. The oxidation of methylcyclohexane gave rise to the isomeric ketones and unusual distribution of alcohol isomers.

Catalysts of Pt/ x %Nb 2 O 5 /Al 2 O 3 (where x = 0, 1, 5, 10, 20 or 100) + Amberlyst 15 were evaluated through the reaction of glycerol hydrogenolysis in a batch system at 413 K and 50 bar of H 2 , with the aim of producing 1,2-propanediol. The supports were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), scanning electron microscopy (SEM) and nitrogen adsorption (surface area – BET and pore size and volume – BJH). Niobia is present as islands on alumina surface, which reduces the interaction between these oxides and favors the creation of Bronsted acidic sites, so that the observed behavior is similar to pure niobia. All systems showed a high yield and selectivity for the production of 1,2-propanediol. The presence of niobia as a support leads to a highly active and selective catalyst for 1,2-propanediol production. The change in the behavior of the active metal can be related to the SMSI effect, inherent to systems containing niobia as support.

A radical mechanism of hydrocarbon oxidations with the environmentally friendly and cheap homogeneous nontransition metal system [Al(H(2)O)(6)](3+)/H(2)O(2)/MeCN-H(2)O was proposed for the first time on the basis of DFT calculations. A dramatic activation of H(2)O(2) toward homolysis in the key intermediate [Al(H(2)O)(4)(OOH)(H(2)O(2))](2+) due to the presence of the easily oxidizable OOH coligand provides, without a change of metal oxidation state, the generation of HO(•) radicals, which then oxidize hydrocarbons. Nonradical mechanisms of the olefin epoxidation with the same catalytic system were also investigated.

Two manganese-containing catalysts have been employed in the oxidation with hydrogen peroxide of two reactive alcohols (1-phenylethanol and glycerol): soluble catalyst [LMn(μ-O)3MnL](PF6)2 (1a) and heterogenized catalyst [LMn(μ-O)3MnL]2[SiW12O40] (1b) (L is 1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN). Oxidation of 1-phenylethanol catalyzed by 1a in acetonitrile solution proceeds at room temperature in the presence of a small amount of oxalic acid; the turnover number attains 15,000 after 3 h. It has been proposed on the basis of the kinetic study that an oxidizing species is a manganyl species containing fragment “Mn=O” rather that hydroxyl radical. This species reacts competitively with the alcohol, acetonitrile and hydrogen peroxide. In the case of 1b dependences of the initial rates of acetophenone accumulation on concentration of the alcohol and amount of 1b have plateau. Both homogeneous and heterogeneous catalysts are efficient in the oxidation of glycerol to produce dihydroxyacetone (DHA) as the main product. The oxidation catalyzed by 1a is one of the first examples of the glycerol oxidation by a catalytic homogeneous system. The yield of valuable products attained 45%. The oxidation of DHA in the absence of glycerol afforded mainly glycolic acid in yield 60% based on the starting DHA. The oxidation on 1b represents the first example of the glycerol transformation catalyzed by a heterogenized metal complex. Under certain conditions yields of products of deeper oxidation (glyceric, glycolic and hydroxypyruvic acids) are somewhat higher than the yield of dihydroxyacetone. Special experiments demonstrated that no leaching of active species occurs from catalyst 1b to the solution and that this catalyst can be re-used at least four times without substantial loss of activity. Manganese-containing complexes are very efficient catalysts in the oxidation of reactive alcohols (1-phenylethanol and glycerol) with H2O2: soluble [LMn(O)3MnL](PF6)2 and heterogenized [LMn(O)3MnL]2[SiW12O40] (L is 1,4,7-trimethyl-1,4,7-triazacyclononane).

The homogeneous catalytic system composed of the aqua-soluble tetracopper(II) triethanolaminate complex [ O ⊂ Cu 4 { N ( CH 2 CH 2 O ) 3 } 4 ( BOH ) 4 ] [ BF 4 ] 2 (1), t-BuOOH (TBHP), water and acetonitrile solvent (optional) has been applied for the mild oxidation of (i) linear and cyclic alkanes to the corresponding alkyl peroxides, alcohols and ketones, (ii) secondary or primary alcohols to ketones or aldehydes, respectively and (iii) glycerol (GLY) to dihydroxyacetone (DHA). Unusual regio-, bond and stereoselectivity parameters have been determined for the alkane oxygenations and discussed in terms of possible steric, hydrophobic and electronic effects. In alcohol oxidations, secondary alcohols are the most reactive substrates. Yields and TONs up to 82% and 1200, respectively, have been obtained in the oxidation of isopropanol to acetone. The selective oxidation of GLY to DHA by the 1/TBHP system has been also achieved, although providing lower conversions. The 1/H2O2 system for the GLY oxidation is particularly advantageous in terms of selectivity and oxidant efficiency. These systems constitute one of the first examples of a metal-catalyzed oxidation of glycerol under homogeneous conditions.

Mesoporous titanium-silicate Ti-MMM-2 catalyzes oxidation of alkanes (cyclooctane, n-heptane, n-octane, isooctane, methylcyclohexane, cis- and trans-1,2-dimethylcyclohexane) and olefins (cyclooctene, 1-decene, (S)-limonene) by H2O2 in acetonitrile solution at 60 °C. The catalytic reaction is truly heterogeneous in nature. The oxidation occurs via the formation of a ‘Ti–OOH’ species on the catalyst surface which either epoxidizes a nucleophilic double bond or generates, after O–O bond splitting, hydroxyl radical. The HO radical attacks an alkane or olefin C–H bond producing alkyl radical. The reaction R + O2 → ROO leads to the formation of alkyl hydroperoxide as the main product of the alkane oxidation. In the case of alkenes this reaction leads to allylic oxidation products. The composition of products of the olefin oxygenation (the epoxide/alkyl hydroperoxide or epoxide/diol ratios, etc.) strongly depends on the nature of the substrate. In the oxidation of (S)-limonene, isomeric diepoxides are formed along with monoepoxides even at the early stage of the reaction and (SRR)-diepoxide predominates among other products. This can be rationalized by suggesting the epoxidation of the two double bonds to occur simultaneously on two adjacent ‘Ti–O–OH’ centers on the catalyst surface.

Montmorillonites K-10, Na0.60K0.12Ca0.02(Al1.78Fe0.12Mg0.10)oct(Si3.89Al0.11)tetO10(OH)2, and NT-25, Na0.10K0.04Ca0.08(Al1.28Fe0.45Mg0.28)oct(Si3.94Al0.06)tetO10(OH)2, and aluminum oxide, Al2O3, catalyze alkane hydroperoxidation and olefin epoxidation with hydrogen peroxide. Alkanes afford alkyl hydroperoxides as main primary products which partially decompose to produce corresponding ketones and alcohols. The oxidation of cis- and trans-isomers of 1,2-dimethylcyclohexane on K-10 proceeds stereoselectively. Benzene in the presence of montmorillonite K-10 is transformed into phenol. Styrene is oxidized to afford benzaldehyde and styrene epoxide. It is proposed on the basis of a kinetic study and measurements of the selectivity parameters that in the case of alumina the oxidation occurs with the participation of hydroxyl radicals generated from an aluminum peroxo derivative on the catalyst surface. In the cases of montmorillonites iron centers are also responsible for the H2O2 activation which gives hydroxyl radicals. Addition of trifluoroacetic acid (TFA) leads to the noticeable acceleration of all oxidation reactions and enhancement of the product yield. It has been shown that in the presence of TFA some parts of solid catalysts are transferred into the homogeneous solution. Thus, very cheap natural solid materials provide soluble species that are active in efficient homogeneous oxidations of hydrocarbons with hydrogen peroxide. In the absence of TFA the oxidation reactions in the case of the three catalysts are truly heterogeneous in nature.

The first example of alkane oxygenation with hydrogen peroxide catalyzed by a non-transition metal derivative (aluminium) is reported. Heating (70 °C) a solution of an alkane, RH, hydrogen peroxide (70% aqueous) and a catalytic amount of Al(NO 3 ) 3 ·9H 2 O in air for a few hours afforded the corresponding alkyl hydroperoxide, ROOH. With cyclooctane, the hydroperoxide yield attained 31% and the maximum turnover number was 150. It is proposed on the basis of measurements of the selectivity parameters for the oxidation of linear and branched alkanes and a kinetic study that the oxidation occurs with the participation of hydroxyl radicals.

Hydrogen peroxide oxidation of cyclohexane in acetonitrile solution catalyzed by the dinuclear manganese(IV) complex [LMn(O)3MnL](PF6)2 (L=1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN) at 25 °C in the presence of a carboxylic acid affords cyclohexyl hydroperoxide as well as cyclohexanone and cyclohexanol. A kinetic study of the reactions with participation of three acids (acetic acid, oxalic acid, and pyrazine-2,3-dicarboxylic acid, 2,3-PDCA) led to the following general scheme. In the first stage, the catalyst precursor forms an adduct. The equilibrium constants K1 calculated for acetic acid, oxalic acid, and 2,3-PDCA were 127±8, (7±2)×104, and 1250±50 M−1, respectively. The same kinetic scheme was applied for the cyclohexanol oxidation catalyzed by the complex in the presence of oxalic acid. The oxidation of cyclohexane in water solution using oxalic acid as a co-catalyst gave cyclohexanol and cyclohexanone, which were rapidly transformed into a mixture of over-oxidation products. In the oxidation of cyclohexanol to cyclohexanone, varying the concentrations of the reactants and the reaction time we were able to find optimal conditions and to obtain the cyclohexanone in 94% yield based on the starting cyclohexanol. Oxidation of acetone to acetic acid by the system containing oxalic acid was also studied.